1. Field of the Invention
This invention relates to an expandable irrigation controller for controlling operation of an irrigation system pursuant to a watering schedule that may be programmed by a user. More particularly, this invention relates to an expandable irrigation controller for controlling multiple irrigation stations.
2. Description of the Related Art
Over the past decade modular expandable irrigation controllers have gained increasing popularity although they have been in commercial use dating back into the 1970's or earlier; i.e. such as the Toro Golf Course Satellite Irrigation Controller. The base portion of these controllers typically contains the programmable logic portion, or microprocessor and user actuated controls.
Each watering station is then preferably controlled by a corresponding module that includes electronically controllable station on/off switching circuitry. The modules are preferably connected to a plurality of irrigation control valves in the irrigation system at each of a plurality of watering stations. These valves are typically solenoid activated. Generally, each module can independently control more than one watering station.
The modules shown in the prior art Toro Golf Course Satellite Irrigation Controller each controlled 8 stations with four 8-station modules installed and another 4 positions for a total of 8 station modules in the same weather resistant enclosure. Some other expandable controllers show various arrangements of “slots” or “cavities” for accommodating modules of a selected size.
The modules typically contain pins, sockets, card edge connectors, or some other standard form of electromechanical connectors that allow them to be inserted into the slots or receptacles in either the housing that contains the microprocessor or a separate portion connected to the microprocessor housing. The advantage of this configuration is that the controller can be provided with a minimum number of modules suitable for control of the total number of watering stations in the system at first, yet can economically and easily be expanded if the need for more watering stations later occurs. Thus, for example, an irrigation system may have only three zones, requiring only a single station module, while another may have twelve stations, which might require four 3-station modules. Considerable cost savings are thus achieved. Moreover, if an irrigation system expands after initial installation because the landscaping has increased, additional station modules can be added without having to replace the entire controller.
Since station output switching circuits may be damaged in service by lightning or over-load current, over time, the damaged circuitry can be replaced by simply replacing a module without the effort or expense of replacing or removing for service the entire irrigation controller.
In the prior art, however, there are slots, cavities or mounting pads for selected size modules to go into selected locations. Modules of the same size are often interchangeable in that the “slots”, “cavities” or “pads” are of the same size. However, this means that the modules must be installed into slot cavities or onto pads that are large enough to accommodate the number of watering stations that they will power. Smaller modules would not fit into the slots, cavities etc., or would be loose and not mounted properly, which may affect proper contact. Thus, there is limited flexibility as to the size of the modules, and consequently, the number of watering stations they may control.
The new Toro TMC-424 controller does not provide for wider modules in order to accommodate additional terminals for station control, but adds more rows of terminals on same width station expansion module so that they can fit into same slots or cavities. Thus, size of the modules is still limited.
In some cases, only 2 station module slots or cavities are shown. Thus, to get 8 station outputs or terminals, the customer must purchase 4 two station modules. This may be more expensive than purchasing 2 four-station modules or 1 eight-station module. When additional expansion is required, one must add modules of a size allowed for by the pre-existing slots or cavities of the controller housing.
The new Toro Controller TMC-424 uses station expansion modules that fit ting sized cavities or slots, but adds more terminals to each module in double rows. However, as noted above, this limits flexibility with regard to the size of the modules that may be used to expand the number of watering stations controlled by the controller, which may result in higher costs.